We propose to determine how infection by viruses such as poliovirus results in specific inhibition of translation of host messenger RNA. We plan to determine the function in protein synthesis of methylated bases at the 5' end of most viral and cellular mRNAs and to isolate and sequence the ribosome attachment site of poliovirus RNA, vesicular stomatitis viral mRNAs, tumor virus RNAs, and Sindbis virus mRNA. These will be compared with the N-terminal sequences of the viral proteins which we are determining. Finally, we are interested in the mode of biogenesis of viral and cellular membranes. We will study why polysomes containing mRNAs encoding viral glycoproteins uniquely are bound to cellular membranes, how viral glycoproteins are inserted into the membrane, how other viral proteins are assembled into the membrane, and how the final particle is assembled. Similar studies will be done on the biosynthesis of the major proteins in the erythrocyte membrane; additionally we will determine the cell stages which make these proteins. Much of this work utilizes cell-free protein synthesis to analyze the function of viral mRNAs. We propose to enhance the efficiency of current mammalian cell-free systems and complete our analysis of cell-free translation of murine leukemia virus RNA.